1. Field of the Invention
The present invention relates to a filter apparatus which is mounted on an internal-combustion engine, particularly on a diesel engine, that captures and removes particulates such as soot exhausted from the engine so as to purify the exhaust gas, thereby preventing environmental pollution.
2. Description of Prior Art
The exhaust of particulates from diesel engines has recently been controlled because it contains carcinogens and because it causes a deterioration in visibility. As a measure against such exhaust particulates, a method has been investigated in which a heat-resistant filter is provided in an intermediate position of an exhaust pipe to remove particulates by filtering them out. This method is characterized by a filter element which can be regenerated and repeatedly used by being incinerated after particulates have been accumulated therein. There have been many proposals in which a burner for regenerating the filter is provided upstream of the filter element to ensure that the temperature of the exhaust gas is increased to the ignition temperature of the particulates by using the combustion heat of the burner. Such a method must increase the temperature of a large amount of gas exhausted from the engine, and thus it requires an enormous quantity of heat.
There has also been a proposal for solving the above-described problem in which the route of exhaust gas is branched at a filter element, and a bypass that is separated from the filter element is provided therein so that the exhaust gases from the engine are passed through the bypass by a valve when the burner is operating. This method obviates the need for heating a large amount of exhaust gas (Japanese Patent Laid-Open No. 118514/1981). This apparatus is provided with a bypass in the filter element of the exhaust gas route and exhausts the gas through the bypass during regeneration, thereby reducing by half, the effect of controlling the exhaust of particulates.
In addition, an apparatus has been proposed in which an exhaust gas inlet of a filter element is divided into two portions and is provided with a switching plate in such a way that the filter element is divided into a regeneration side and an exhaust gas side by the switching plate during regeneration (Japanese Patent Laid-Open No. 101210/1983). In this apparatus, since the regeneration portion and the portion through which the exhaust gas flow coexist in the one filter during regeneration, large thermal stresses occur, which readily lead to the fracture of the filter element.
Prior art with respect to a combustion apparatus for vehicles is also described in Japanese Patent Laid-Open No. 11415/1986.